Oil Spill Cleanup: The Sand Berm Controversy

Officials in Louisiana continue to push for a 6-foot sand berm that, if effective, could protect fragile marsh ecosystems from offshore oil that has yet to reach the shores. But the plan has its critics.

Tidal marshes in Louisiana are some of the most delicate ecosystems in the Gulf of Mexico, where offshore oil continues to wash ashore. To protect cord grasses, shrimp larvae and terrapin turtles, local government officials are promoting a number of short-term infrastructure projects, including a $360 million proposal to build sand berms along 125 feet of barrier islands surrounding the Mississippi Delta, a controversial engineering feat.

Louisiana received approval to build multiple 6-foot-high, 300-foot-wide berms along 45 miles of the coastline, but when contractors began dredging for sand, federal officials stopped the project, saying that they were getting the material from sensitive areas. That sand is only available in limited supplies and when it's dredged and used for this project, it may not be there for long-term restoration projects, federal scientists argue. Now that the berms are again under construction. Louisiana Governor Bobby Jindal is celebrating their success, saying they're working as planned, while others, including marine scientists, say they're failing.

But not all areas are dredge-sensitive. "There are areas where, if you remove sand, you're not affecting the environment around it," says James Flocks, a geologist with the USGS who reviewed the proposal. One of the approved stretches of berm is east of the Mississippi River along the Chandeleur Islands. Wave action moves the sand on the shoreline north, so "taking sand from that area and putting it back near the Chandeleurs would create a sort of sand conveyor belt. We consider that a safe area to remove sand from," Flock says. Taking the sand from the islands themselves, however, could yield material, but only at the expense of the isles' structure.

Others argue that no matter where you dredge, the project could create deeper troughs in the seabed, causing waves to hit the berm with greater strength. Waves traveling over deeper seas grow bigger until they reach the beach. When they crash on shore, they do so with more force and energy than those that roll over shallower bottoms. "The erosion potential is increased as a function of dredging. What it is that you're trying to preserve along the coast is actually going to experience higher and more erosive wave conditions," says Gregory Stone, director of the Coastal Studies Institute at Louisiana State University.

If the berms are built in time, they could protect oil from getting on the beaches, but chances are slim that they will protect the marshes, Flock says. The berms will need to be designed to maintain the tidal flow, he says, so oil could get in through the channels created for this. Furthermore, the berms themselves are fragile. Even if the oil continues to bubble after the berms are completed, a hurricane could wash them away and fundamentally change the structure of the beaches.

If the berms collect oil as they should (without an intervening hurricane), the job is far from over. When berms collect and hold the sand, the granules will become contaminated with the sticky stuff. The oil that's coming to land, or to the berm, is much more weathered and viscous than the variety studied in other spills. It resembles tar or asphalt, and is resistant to microbial breakdown, says John Fleeger, a biologist at Louisiana State University. Oiled debris, including sand-encrusted tar balls, were tested by BP and determined to be non-hazardous, so they're collected by the Louisiana National Guard and taken to a landfill.

The plethora of variables makes it difficult to predict what's going to happen to the coastal and salt marsh environments, frustrating scientists like Fleeger: "The berm does offer some promise to reduce the oil entering into the salt marshes. The problem is that we don't know the full picture."